Tens of thousands of demonstrators, most of them Sunni, have marched and blocked roads in the last week over discrimination and alleged Government suppression of the religious minority.

Sadr told reporters in the Shiite holy city of Najaf that the demonstrators have the right to protest as long as they are peaceful. He said that al-Maliki “bears full responsibility” for the discontent.

The Sadrists backed al-Maliki following elections in 2010, then last year joined Iraq’s minority Sunni Arabs and Kurds in calling for the Prime Minister to resign. The bloc holds 40 seats in parliament and retain control of several government ministries.

"There have been continued attempts by opposition militants to target civilian aircraft, which could cause a humanitarian disaster," an airport official asserted. He said the airport would be closed for a "very short period of time" while the army tried to regain control of surrounding areas.

Syria's national airline began cancellation of some flights to the airport on Sunday.